Overview

Linux 6.19 is another release packed with significant changes. From a mechanism for updating the kernel without restarting virtual machines, through a new system call, to major filesystem and scheduler improvements. Here are the highlights.

Live Update Orchestrator (LUO)

The biggest news in this release. LUO is a kernel subsystem enabling kernel updates via kexec while preserving resource state. In practice, this means virtual machines can continue running during a host kernel swap with minimal downtime.

This is a massive change for cloud and virtualization environments, where updating the host kernel previously required migrating or restarting all VMs.

New System Call: listns(2)

The new syscall allows enumerating namespaces without scanning /proc. It offers pagination, filtering, and permission checking. This is a much more efficient approach than parsing procfs, especially on systems with thousands of containers.

Filesystems

Btrfs

  • Shutdown ioctl — experimental controlled filesystem shutdown support
  • Async checksum — parallel checksum calculation (better performance)
  • Scrub improvements — suspend and resume scrub/device replacement with state preservation
  • Fscrypt preparations — groundwork for filesystem-level encryption

ext4

  • Block sizes larger than page size — support for blocks >4K
  • Faster online defragmentation — ~50% write performance improvement during defrag
  • Better Direct I/O — increased throughput for direct operations

NFS

  • Direct I/O read — direct reads over NFS
  • Better write performance — via the NFSD_IO_DIRECT option
  • Directory delegations — new module option

Memory and Resource Management

  • Device-Private THP — Transparent Huge Pages on device memory (GPUs)
  • NUMA mempolicy for KVM — NUMA affinity for KVM guest memory
  • Dmabuf-iommufd — GPU memory buffer integration with IOMMU
  • ECC handling — error correction for pages without struct page metadata

io_uring

io_uring continues to evolve:

  • Mixed-size SQEs — submission queue entries can now have different sizes
  • Zcrx: multi-ring — sharing hardware RX queue infrastructure across multiple rings
  • getsockname/getpeername — new socket operations
  • SQ/CQ layout queries — for user-provided rings

Scheduler

  • NEXT_BUDDY for EEVDF — reintroduction of the “next buddy” mechanism in the EEVDF scheduler
  • Proportional newidle balance — load balancing optimization
  • Rewritten MM CID — new memory context ID management
  • sched_ext — improved bypass mode scalability

Graphics and Drivers

  • Color Pipeline API — new API for color transformations, key for HDR support on Linux
  • Sharpness property — adaptive sharpness filtering (Intel Lunar Lake+)
  • Arm Ethos NPU — ARM neural processing unit accelerator driver
  • AMD SI/CIK — Vulkan support for older AMD discrete cards

Tracing and Debugging

  • SFrame — new stack unwinding format, significantly faster than DWARF with minimal performance overhead
  • CONFIG_DEBUG_BUGVERBOSE_DETAILED — WARN_ON_ONCE() now prints the condition that was triggered — easier debugging
  • klp-build — script for generating livepatch patches with objtool

Rust in the Kernel

The Rust ecosystem in the kernel continues to grow:

  • Abstractions for the PWM subsystem (with the first th1520 driver)
  • Basic I2C driver abstractions
  • Bounded integer types
  • Module parameter support for integers
  • Binary large objects for debugfs

Security

  • PCIe link encryption — secure communication for confidential VMs, encrypting traffic between VM and device
  • Uaccess scopes — new scope-based user memory access management, improving safety
  • CPU System Wakeup QoS — new interface for specifying wakeup quality-of-service limits

Summary

Linux 6.19 is a strong release. The Live Update Orchestrator changes the game for cloud and virtualization. Btrfs and ext4 improvements boost everyday performance. The Color Pipeline API opens the door to full HDR on the desktop. And the Rust ecosystem in the kernel becomes more functional with every release.

Full changelog: kernelnewbies.org/Linux_6.19